Apparatus for shrinking plastic film over palletized loads

ABSTRACT

An apparatus for shrinking an overwrap material, such as a plastic material exhibiting preferential shrink properties, over an article to be encapsulated wherein structural members are provided to support heating elements to preferentially heat portions of the plastic overwrap material to shrink it about the article. The structural members are adapted to traverse the article to be encapsulated to pass the heating elements over the overwrap to cause the overwrap material to shrink about the article thereby to encapsulate the article tightly within the overwrap material.

[ 1 Jan. 16, 1973 United States Patent 1 Osborne 0 3 N 5 sm Nm mw Tm W w m Lm Pm D." Am Rm om S m W0 T. m NH G6 E R1 mm 4 w Primary Examiner-Robert L. Spruill Attorney-Curtis, Morris & Safford Keith J. Osborne, 2167 B North Central Road, Fort Lee, NJ. 07024 Dec. 3, 1970 7] ABSTRACT An apparatus for shrinking an overwrap material, such [22] Filed:

[21] Appl. No.: 94,646

as a plastic material exhibiting preferential shrink properties, over an article to be encapsulated wherein structural members are provided to support heating elements to preferentially heat portions of the plastic an HUN 359 5&4, 7 B mm4 00 mm4 m MWO 3 ""3 W mh c "MM m e m .L M C WM .t e Umh lll. 2 8 555 [[(l overwrap material to shrink it about the article. The structural members are adapted to traverse the article to be encapsulated to pass the heating elements over [56] References Cited UNITED STATES PATENTS the overwrap to cause the overwrap material to shrink about the article thereby to encapsulate the article tightly within the overwrap material.

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sum 1 or 3 INVENTOR. KEITH J.OSBORNE PATENTEDJAH 16 I973 3.710.550

sum 2 OF 3 I N V ['1 N 'I OR KEITH J. OSBORNE PATENTEDJAH 16 I975 3.710.550

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KEITH J.OS8ORNE ATTORNEYS APPARATUS FOR SHRINKING PLASTIC FILM OVER PALLETIZED LOADS The present invention relates to overwrap shrinking apparatus and more particularly to overwrap shrinking apparatus adapted to shrink a plastic over large articles, for example a load stacked on a pallet.

When packaging large loads of goods, for example a palletized load wherein a number of cartons are stacked one on top of another on a pallet, it is often desirable to enclose the palletized load for ease in shipment and/or to prevent pilferage during transit and one method to enclose such loads has been to encapsulate the palletized load within a plastic covering. One method for encapsulating a palletized load is disclosed in US. Pat. No. 3,429,095 to Huson wherein a plastic bag is placed over the palletized load and air is evacuated from within and the plastic covering material is then strapped to the load. Another method for encapsulating a load is shown in Myers U.S. Pat. No. 3,508,375 wherein a bag of heat shrinkable material is placed over a palletized load, air is evacuated from within and the plastic covered palletized load is passed through an oven enclosure to heat shrink the plastic bag over the load.

Both of these methods while generally satisfactory to encapsulate a palletized load have certain inherent deficiencies. In the method disclosed in the Huson patent, the plastic overwrap is not being shrunk and, hence, the encapsulated load after being strapped has an excess of the plastic material which may be ripped or cut during normal handling of the palletized load in transit thus destroying the integrity of the encapsulated package. In the method disclosed in the Myers patent, the requirement of an oven in order to heat shrink the plastic overwrap material limits the flexibity of the overwrap system.

It is therefore an object of the present invention to provide an apparatus for heat shrinking a plastic film or overwrap over a large load of goods in an efficient and economical manner.

It is another object of the present invention to provide an apparatus to heat shrink a plastic overwrap over a load of goods by using infrared heating elements to penetrate the heat film and enable the specific film characteristics to be used to their fullest extent to obtain maximum and uniform shrinkage of the overwrap in the shortest possible time.

It is a further object of the present invention to provide an apparatus for heat shrinking a plastic overwrap over a load of goods which can be readily adjusted to conform to loads of varying sizes.

It is yet a further object of the present invention to provide apparatus for heat shrinking a film of plastic material over a load of goods which can be readily knocked down for shipping and/or reassembly.

These and other aspects and advantages of the present invention will be more readily understood after consideration of the following specifications and drawings.

In the drawings:

FlG. 1 is a perspective view of the apparatus of the present invention;

FIG. 2 is an elevational view taken along line 22 of FIG. 1; and

FIGS. 3-6 are diagrammatic representations of the sequence of operations of the heat shrink apparatus of the present invention in a typical assembly line operation.

In accordance with a preferred embodiment of the present invention, infrared heating elements are ad- 5 justably mounted on the upstanding leg portions of a pair of U-shaped gantries. An overhead support structure includes means to slidably mount the bight portion of one of the gantries and the other gantry includes means at the lower end of its leg member for slidable disposition along a support surface. The two gantries are disposed at to one another and are adapted to reciprocate along a limited path so that the planes within which each of the upstanding leg members and the bight portion of at least one of the gantries reciprocate define an article receiving area within which a pallet load of goods to be encapsulated is placed. The infrared heating elements carried by the gantries thus traverse the loaded pallet covered with a pre-formed bag of heat shrinkable plastic material thereby to shrink the plastic bag snugly about the loaded pallet.

With reference to the drawings and particularly FIG. 1, there is shown the heat-shrink apparatus of the present invention comprising a pair of U-shaped gantry members 12 and 14, respectively. Gantry 12 includes a pair of substantially vertically disposed leg members 16 interconnected by a substantially horizontal bight portion 18 and gantry 14 includes a pair of upstanding leg members 20 interconnected by a substantially horizontal bight portion 22.

The lower ends of the leg members 20 are provided with rollers 24 adapted to ride along a pair of guide tracks 26. Rollers 24 are driven by a reversible motor (not shown) carried by upstanding leg members 20 so that gantry 14 is reciprocably powered for movement along guide tracks 26.

An overhead support structure 28 is provided including spaced upstanding vertical leg members 30 which support a horizontal cross piece 32 which preferably may be an l-beam having its flange members 34 (see FIG. 2) horizontally disposed. The bight portion 18 of gantry 12 is provided with an integral housing 36 on its upper side to mount roller members 38 adapted to roll along flange 34 of cross piece member 32. These roller members 38 are also powered by a reversible electric motor (not shown) so that gantry 12 can reciprocably traverse along a path of movement parallel to the longitudinal axis of cross piece member 32.

As seen in FIGS. 1 and 2, the vertical leg members 16 of gantry 12 are longer than the vertical leg members 20 of gantry 14 so that there is a clearance between bight portion 18 and bight portion 22 of the respective gantries. This provides a clearance between the two gantries when each of them are reciprocated along their respective guide tracks.

Each of the vertical leg members 16 and 20 and bight portions 18 and 22, respectively, of the gantries 12 and 14 move in respective planes as the gantries reciprocate along their guide tracks and these planes define an article receiving area 40 within which an article or load to be encapsulated, such as a pallet 42 loaded with stacked boxes of goods 44, may be received. In operation, the loaded pallet 42 after being covered with a pre-formed bag 48 of heat shrinkable material such as polyethylene, polypropylene, polyvinylchloride or a polyolefin is conveyed by a takeoff conveyor 46 to the pallet receiving area 40.

Each of the upstanding leg members 16 and of the gantries 12 and 14, respectively, as well as bight portion 22 of gantry 14 are provided with heating elements on their inner sides thereof to direct heat toward the loaded pallet 42 to shrink the covering 48 about the loaded pallet as the gantries traverse the loaded pallet in the pallet receiving area 40. Gantry 12 is provided with vertical banks of heating elements 50 secured to upstanding legs 16 and gantry 14 is provided with vertical banks of heating elements 52 secured to the upstanding legs 20 and a horizontal bank of heating elements 54 secured to the bight portion 22. Preferably, the heating elements 50, 52 and 54 are infrared type heating elements which emit infrared rays to penetrate the plastic covering material 48 to shrink the film about the loaded pallet and encapsulate the load.

As best seen in FIG. 2, each of the banks 50, 52 and 54 of infrared heating elements are comprised of a plurality of individual heating elements 56 mounted to the respective gantries 12 and 14 by extensible mounting brackets 58, which mounting brackets may be of the lazy-tong variety. In this manner, all, or selective ones of the individual heating elements 56 may be extended away from the respective gantries 12 or 14 in order to accommodate pallet loads of various sizes as well as of differing shapes in order to bring the heating elements in relative close proximity to the pallet load.

While the heating elements 56 are shown secured to their respective gantries by extensible lazy-tong mounting brackets 58, it is readily understood that any other extensible means, such as pneumatically actuated cylinders or electric motors driving a gearing mechanism can be employed to selectively extend one or more of the individual heating elements 56 away from the gantry upon which it is supported. In like manner, it is to be understood that the gantries themselves can be made to traverse their respective reciprocable paths of movement by other appropriate means, for example pneumatically actuated cylinders,

hydraulic actuators or electrically driven geared mechanisms.

In a preferred arrangement for production line operation, the pallet takeoff conveyor 46 (see FIGS. 3-6) is arranged so as to selectively takeoff one pallet load 42a to be encapsulated covered with a heatshrinkable pre-formed plastic bag 48 from conveyor system 47 which is loaded with a series of similar pallet loads 42b,c, etc. Takeoff conveyor 46 conveys the single pallet load 42a to the heat-shrink station 40 while the remaining series of pallet loads 42 are retained on the main conveyor by an appropriate conveyor blockage mechanism 60. For an initial pallet load 42a, the gantries l2 and 14 are in one extreme position of their reciprocable path of movement as shown in FIG. 3 and after the pallet load 42a has been admitted to the heat-shrink station 40 the gantries l2 and 14 traverse the pallet load 42 in the direction of the arrows as shown in FIG. 4, until the gantries have moved to their other extreme position as shown in FIG. 5.

After the gantries l2 and 14 have traversed a pallet load 42a in shrink station 40, the gantries are stopped and the takeoff conveyor is actuated to remove the pallet Ioad'42a upon which the plastic material has been shrunk from the shrink station 40 and the next pallet load 42b to be shrunk is admitted to station 40. The shrink process is enacted from the gantry position shown in FIG. 5 as the gantries move in the direction of the arrows shown in FIG. 6 toward the position of the gantries shown in FlG.'1. Thus, shrinking occurs each time the gantries move to eliminate wasted motion and the apparatus shrinks the overwrap over one pallet as the gantries move in one direction and shrink the overwrap over the next pallet as they move in the opposite direction.

The infrared heating elements 56 carried by the respective gantries 12 and 14 may be used in a continuous mode, i.e., continuously emitting infrared radiation as the gantries traverse the pallet load or the infrared heating elements may be pulsed as the gantries traverse the pallet load as desired. In high production line operations it would be preferable to have the gantries traverse the pallet load as rapidly as possible while the infrared heating elements are in a continuous mode and in low volume operations the speed of the gantry traverse can be slowed and the infrared elements pulsed for greater economy.

It is thus seen that the apparatus of the present invention provides a readily adaptable device to encapsulate a pallet loaded with goods or any large irregularly shaped object by shrinking a plastic bag of polyethylene, polypropylene, polyvinylchloride, a polyolefin or the like by utilizing infrared heat elements which are made to traverse the article or articles to be encapsulated inorder to preferentially and selectively shrink the plastic material over the load to be encapsulated.

What is claimed is:

1. In an apparatus for shrinking a heat-shrinkable overwrap material over an article to be encapsulated, the combination of,

first and second upstanding U-shaped gantry members each said gantry including upstanding leg members and a connecting bight portion,

said gantries being disposed at approximately to one another with the bight portion of said first gantry overlying the bight portion of said second, means adapting each said gantry for simultaneous reciprocable movement along a limited path of movement,

heating elements fixed to the upstanding leg members of each said gantry and to the bight portion of said second gantry, v

the respective planes within which each of said upstanding leg members and said second gantry bight portion moves defining an article receiving area therebetween, I I means to selectively transport an article covered by an overwrap of heat-shrinkable material into said article receiving area wherein as said gantry members traverse said article receiving area said heating elements heat-shrink said overwrap material about said article. I 2. Apparatus as defined in claim 1 wherein said heating elements are infrared heating elements and said overwrap material is a material selected from the group consisting of polyethylene, polypropylene, polyvinylchloride, and a polyolefin.

thereof adapted to ride on spaced guide track members to facilitate the reciprocable movement of said second gantry along said guide track members.

5. Apparatus as defined in claim 4 including a support structure having a horizontal segment disposed above said first gantry bight portion, said first gantry bight portion including means engaging said horizontal segment for slidable disposition therealong whereby said first gantry member is slidably retained on said support structure. 

1. In an apparatus for shrinking a heat-shrinkable overwrap material over an article to be encapsulated, the combination of, first and second upstanding U-shaped gantry members each said gantry including upstanding leg members and a connecting bight portion, said gantries being disposed at approximately 90* to one another with the bight portion of said first gantry overlying the bight portion of said second, means adapting each said gantry for simultaneous reciprocable movement along a limited path of movement, heating elements fixed to the upstanding leg members of each said gantry and to the bight portion of said second gantry, the respective planes within which each of said upstanding leg members and said second gantry bight portion moves defining an article receiving area therebetween, means to selectively transport an article covered by an overwrap of heat-shrinkable material into said article receiving area wherein as said gantry members traverse said article receiving area said heating elements heat-shrink said overwrap material about said article.
 2. Apparatus as defined in claim 1 wherein said heating elements are infrared heating elements and said overwrap material is a material selected from the group consisting of polyethylene, polypropylene, polyvinylchloride, and a polyolefin.
 3. Apparatus as defined in claim 1 wherein said heating elements fixed to each said upstanding leg members and to said second gantry bight portion comprise a plurality of individual heating units and include extensible and retractable means for mounting each said heating unit on said respective gantry member whereby said individual heating units may be selectively extended away from and retracted toward said gantry member to accommodate articles of varying sizes.
 4. Apparatus as defined in claim 1 wherein said second gantry includes roller members carried by the upstanding leg members at their lowermost ends thereof adapted to ride on spaced guide track members to facilitate the reciprocable movement of said second gantry along said guide track members.
 5. Apparatus as defined in claim 4 including a support structure having a horizontal segment disposed above said first gantry bight portion, said first gantry bight portion including means engaging said horizontal segment for slidable disposition therealong whereby said first gantry member is slidably retained on said support structure. 